Anti-Tn-MUC1 Antibodies
The human mucin MUC1 is a polymorphic transmembrane glycoprotein expressed on the apical surfaces of simple and glandular epithelia. MUC1 is highly overexpressed and aberrantly O-glycosylated in adenocarcinomas. The extracellular domain of the mucin contains variable number of tandem repeats (25-125) of 20 amino acid residues with five potential sites for O-glycosylation. O-glycans are incompletely processed in cancer cells resulting in the expression of the pancarcinoma carbohydrate antigens Tn (GalNAcα1-O-Ser/Thr), STn (NeuAcα2-6GalNAcα1-O-Ser/Thr), and T (Galβ1-3GalNAcα1-O-Ser/Thr). MUC1 expressed by breast carcinoma cells carries the short cancer-associated Tn, STn, and T antigens as well as the mono- and disialyl core 1 structure (ST, NeuAcα2-3Galβ1-3[NeuAcα2-6]+/−GalNAcα1-O-Ser/Thr) found widely in normal cells. In contrast, MUC1 expressed in normal breast epithelial cells generally carry branched core 2 O-glycans (Galβ1-3[GlcNAcβ1-6]GalNAcα1-O-Ser/Thr) with lactosamine extensions. The cell membrane bound mucin MUC1 has long been considered a prime target for immunotherapeutic intervention. The existence of anti-MUC1 antibodies and circulating immune complexes containing MUC1 in breast cancer patients that correlates with improved prognosis, clearly supports MUC1 as a target. However, until recently, stimulation of an effective cellular or humoral immune response to cancer-associated forms of MUC1 in patients or transgenic animals expressing the human MUC1 gene (using defined immunogens as opposed to cell based therapies) had not been achieved.
More recent research has demonstrated that immunization with long Tn- or 5Tn-MUC1 tandem repeat glycopeptides can override tolerance in humanized MUC1 transgenic Balb/c mice (Sorensen et al. 2006, and example 1 of WO2008/040362). The humoral immune response induced with the glycopeptide vaccines was highly specific for the Tn/STn-MUC1 glycoforms and MUC1 expressed by human cancer cells. This research was developed, with the same group demonstrating that immunization with an immunogenic glycopeptide comprising a GSTA motif O-glycosylated at least at the T-residue or at the S-residue induces a cancer specific immune response toward MUC1 (WO2008/040362). Examples of antibodies produced using this technique include the mouse monoclonal antibodies “5E5” (secreted by the hybridoma deposited at the European Collection of Cell Cultures (ECACC) on 20 Sep. 19, 2006 under accession number STHM1 06092102) and “2D9” (secreted by the hybridoma deposited at the European Collection of Cell Cultures (ECACC) on Sep. 19, 2006 under accession number STHM2 06092101). The human/mouse mouse version of mouse monoclonal antibody “5E5” (secreted by the hybridoma deposited at the European Collection of Cell Cultures (ECACC) on 20 Sep. 19, 2006 under accession number STHM1 06092102) is herein described as “mouse 5E5”.
Pyrrolobenzodiazepines
Some pyrrolobenzodiazepines (PBDs) have the ability to recognise and bond to specific sequences of DNA; the preferred sequence is PuGPu. The first PBD antitumour antibiotic, anthramycin, was discovered in 1965 (Leimgruber, et al., J. Am. Chem. Soc., 87, 5793-5795 (1965); Leimgruber, et al., J. Am. Chem. Soc., 87, 5791-5793 (1965)). Since then, a number of naturally occurring PBDs have been reported, and over 10 synthetic routes have been developed to a variety of analogues (Thurston, et al., Chem. Rev. 1994, 433-465 (1994); Antonow, D. and Thurston, D. E., Chem. Rev. 2011 111 (4), 2815-2864). Family members include abbeymycin (Hochlowski, et al., J. Antibiotics, 40, 145-148 (1987)), chicamycin (Konishi, et al., J. Antibiotics, 37, 200-206 (1984)), DC-81 (Japanese Patent 58-180 487; Thurston, et al., Chem. Brit., 26, 767-772 (1990); Bose, et al., Tetrahedron, 48, 751-758 (1992)), mazethramycin (Kuminoto, et al., J. Antibiotics, 33, 665-667 (1980)), neothramycins A and B (Takeuchi, et al., J. Antibiotics, 29, 93-96 (1976)), porothramycin (Tsunakawa, et al., J. Antibiotics, 41, 1366-1373 (1988)), prothracarcin (Shimizu, et al, J. Antibiotics, 29, 2492-2503 (1982); Langley and Thurston, J. Org. Chem., 52, 91-97 (1987)), sibanomicin (DC-102)(Hara, et al., J. Antibiotics, 41, 702-704 (1988); Itoh, et al., J. Antibiotics, 41, 1281-1284 (1988)), sibiromycin (Leber, et al., J. Am. Chem. Soc., 110, 2992-2993 (1988)) and tomamycin (Arima, et al., J. Antibiotics, 25, 437-444 (1972)). PBDs are of the general structure:

They differ in the number, type and position of substituents, in both their aromatic A rings and pyrrolo C rings, and in the degree of saturation of the C ring. In the B-ring there is either an imine (N═C), a carbinolamine (NH—CH(OH)), or a carbinolamine methyl ether (NH—CH(OMe)) at the N10-C11 position which is the electrophilic centre responsible for alkylating DNA. All of the known natural products have an (S)-configuration at the chiral C11a position which provides them with a right-handed twist when viewed from the C ring towards the A ring. This gives them the appropriate three-dimensional shape for isohelicity with the minor groove of B-form DNA, leading to a snug fit at the binding site (Kohn, In Antibiotics III. Springer-Verlag, New York, pp. 3-11 (1975); Hurley and Needham-VanDevanter, Acc. Chem. Res., 19, 230-237 (1986)). Their ability to form an adduct in the minor groove, enables them to interfere with DNA processing, hence their use as antitumour agents.
A particularly advantageous pyrrolobenzodiazepine compound is described by Gregson et al. (Chem. Commun. 1999, 797-798) as compound 1, and by Gregson et al. (J. Med. Chem. 2001, 44, 1161-1174) as compound 4a. This compound, also known as SG2000, is shown below:

WO 2007/085930 describes the preparation of dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody. The linker is present in the bridge linking the monomer PBD units of the dimer.
A particularly advantageous pyrrolobenzodiazepine compound is described by Gregson et al. (Chem. Commun. 1999, 797-798) as compound 1, and by Gregson et al. (J. Med. Chem. 2001, 44, 1161-1174) as compound 4a. This compound, also known as SG2000, is shown below:

WO 2007/085930 describes the preparation of dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody. The linker is present in the bridge linking the monomer PBD units of the dimer.
WO 2011/130613 and WO 2011/130616 describe dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody. The linker in these compounds is attached to the PBD core via the C2 position, and are generally cleaved by action of an enzyme on the linker group. In WO 2011/130598, the linker in these compounds is attached to one of the available N10 positions on the PBD core, and are generally cleaved by action of an enzyme on the linker group.
Antibody-Drug Conjugates
Antibody therapy has been established for the targeted treatment of patients with cancer, immunological and angiogenic disorders (Carter, P. (2006) Nature Reviews Immunology 6:343-357). The use of antibody-drug conjugates (ADC), i.e. immunoconjugates, for the local delivery of cytotoxic or cytostatic agents, i.e. drugs to kill or inhibit tumor cells in the treatment of cancer, targets delivery of the drug moiety to tumors, and intracellular accumulation therein, whereas systemic administration of these unconjugated drug agents may result in unacceptable levels of toxicity to normal cells (Xie et al (2006) Expert. Opin. Biol. Ther. 6(3):281-291; Kovtun et al (2006) Cancer Res. 66(6):3214-3121; Law et al (2006) Cancer Res. 66(4):2328-2337; Wu et al (2005) Nature Biotech. 23(9):1137-1145; Lambert J. (2005) Current Opin. in Pharmacol. 5:543-549; Hamann P. (2005) Expert Opin. Ther. Patents 15(9):1087-1103; Payne, G. (2003) Cancer Cell 3:207-212; Trail et al (2003) Cancer Immunol. Immunother. 52:328-337; Syrigos and Epenetos (1999) Anticancer Research 19:605-614).
Maximal efficacy with minimal toxicity is sought thereby. Efforts to design and refine ADC have focused on the selectivity of monoclonal antibodies (mAbs) as well as drug mechanism of action, drug-linking, drug/antibody ratio (loading), and drug-releasing properties (Junutula, et al., 2008b Nature Biotech., 26(8):925-932; Dornan et al (2009) Blood 114(13):2721-2729; U.S. Pat. No. 7,521,541; U.S. Pat. No. 7,723,485; WO2009/052249; McDonagh (2006) Protein Eng. Design & Sel. 19(7): 299-307; Doronina et al (2006) Bioconj. Chem. 17:114-124; Erickson et al (2006) Cancer Res. 66(8):1-8; Sanderson et al (2005) Clin. Cancer Res. 11:843-852; Jeffrey et al (2005) J. Med. Chem. 48:1344-1358; Hamblett et al (2004) Clin. Cancer Res. 10:7063-7070). Drug moieties may impart their cytotoxic and cytostatic effects by mechanisms including tubulin binding, DNA binding, proteasome and/or topoisomerase inhibition. Some cytotoxic drugs tend to be inactive or less active when conjugated to large antibodies or protein receptor ligands.
The present inventors have developed humanised antibodies based on the ‘mouse 5E5’ antibody, along with antibody-drug conjugates comprising the humanised 5E5 antibodies and PBD drug-moieties.